Today's cellular communication systems provide not only voice services, but also mobile broadband services all over the world. As the number of applications for cell phones and other wireless devices continues to increase, consuming increasing amounts of data, an enormous demand for mobile broadband data services is generated. This requires telecom operators to improve data throughput and maximize the efficient utilization of limited resources.
As the spectrum efficiency for the point-to-point link approaches its theoretical limit, one way to increase data throughput is to split big cells into smaller and smaller cells. When the cells become closer to each other, however, proximate and adjacent cell interferences become more severe, and the cell splitting gain saturates. Furthermore, it is becoming more difficult to acquire new sites to install base stations for the operators and the costs are also increasing. Therefore, cell-splitting alone cannot fulfill the demands.
Recently a new type of network deployment referred to as a HetNet (Heterogeneous Network) has been proposed and is attracting interest and considerable effort in the industry. In HetNet, another tier consisting of multiple low-power nodes is added onto the existing macro base station's coverage areas. The low-power nodes are usually deployed in clusters of cells.
The cells of the Low Power Nodes (LPNs) may operate on the same carrier frequency as the macro node, or on different carrier frequencies. In various communication protocols such as 3GPP (the 3rd Generation Partnership Project standard), it has been found that a discovery of these Low Power Nodes is not always possible with the legacy mechanism. Therefore, the introduction of a new discovery signal (DS) is discussed within various communication protocols such as 3GPP.